Jukka Alinikula - Academia.edu (original) (raw)
Papers by Jukka Alinikula
European journal of immunology, 2017
The transcription factor Bach2 is required for germinal center formation, somatic hypermutation (... more The transcription factor Bach2 is required for germinal center formation, somatic hypermutation (SHM), and class-switch recombination (CSR) of immunoglobulins. SHM and CSR are initiated by activation-induced cytidine deaminase (AID) which has potential to induce human B cell lymphoma. To understand the role of Bach2 in AID-mediated immunoglobulin gene diversification processes, we established a BACH2-deficient DT40 B cell line. We show that in addition to allowing SHM, Bach2 drives immunoglobulin gene conversion (GCV), another AID-dependent antibody gene diversification process. We demonstrate that Bach2 promotes GCV by increasing the expression of AID. Importantly, we found that the regulation of AID is independent of Blimp-1 and that BACH2-deficient cells have altered expression of several genes regulating AID expression, stability and function. Furthermore, re-expression of BACH2 or AID in Bach2KO cells restored the SHM and GCV defects. These results demonstrate that Bach2 has a ...
PloS one, 2016
The activation induced cytosine deaminase (AID) mediates diversification of B cell immunoglobulin... more The activation induced cytosine deaminase (AID) mediates diversification of B cell immunoglobulin genes by the three distinct yet related processes of somatic hypermutation (SHM), class switch recombination (CSR), and gene conversion (GCV). SHM occurs in germinal center B cells, and the transcription factor Bcl6 is a key regulator of the germinal center B cell gene expression program, including expression of AID. To test the hypothesis that Bcl6 function is important for the process of SHM, we compared WT chicken DT40 B cells, which constitutively perform SHM/GCV, to their Bcl6-deficient counterparts. We found that Bcl6-deficient DT40 cells were unable to perform SHM and GCV despite enforced high level expression of AID and substantial levels of AID in the nucleus of the cells. To gain mechanistic insight into the GCV/SHM dependency on Bcl6, transcriptional features of a highly expressed SHM target gene were analyzed in Bcl6-sufficient and -deficient DT40 cells. No defect was observ...
B lymphocytes constitute a key branch of adaptive immunity by providing specificity to recognize ... more B lymphocytes constitute a key branch of adaptive immunity by providing specificity to recognize a vast variety of antigens by B cell antigen receptors (BCR) and secreted antibodies. Antigen recognition activates the cells and can produce antibody secreting plasma cells via germinal center reaction that leads to the maturation of antigen recognition affinity and switching of antibody effector class. The specificity of antigen recognition is achieved through a multistep developmental pathway that is organized by interplay of transcription factors and signals through BCR.
Cell, Jan 18, 2014
AID mis-targeting is poorly understood but contributes significantly to B cell genome instability... more AID mis-targeting is poorly understood but contributes significantly to B cell genome instability. Two new papers in Cell reveal that AID mistargeting occurs primarily in gene bodies within a nuclear microenvironment characterized by high levels of transcriptional activity, interconnected transcriptional regulatory elements, and overlapping sense and antisense (convergent) transcription.
Scandinavian Journal of Immunology, 2011
Effective humoral immunity depends on B cells, plasma cells and follicular helper T cells (TFH) a... more Effective humoral immunity depends on B cells, plasma cells and follicular helper T cells (TFH) and secreted high-affinity antibodies. The differentiation of mature B cell into plasma cells is ultimately hardwired in a regulatory network of transcription factors. This circuitry is responding to extracellular stimuli, which leads to production of higher-affinity antibodies after germinal centre (GC) reaction. The understanding of the transcriptional regulation of GCs and the initiation of plasma cell differentiation is becoming increasingly clear. It is evident that transcriptional repressor Blimp-1 can drive the plasma cell differentiation, but the initiation of plasma cell differentiation in GCs is likely coupled to the loss of B cell characteristics maintained by transcription factors Pax5 and Bcl6.
The Journal of Immunology, 2013
Scandinavian journal of immunology, Jan 14, 2015
The graded expression of transcription factor Interferon Regulatory Factor 4 (IRF4) regulates B c... more The graded expression of transcription factor Interferon Regulatory Factor 4 (IRF4) regulates B cell development and is critical for plasma cell differentiation. However, the mechanisms, by which IRF4 elicits its crucial tasks, are largely unknown. To characterize the molecular targets of IRF4 in B cells, we established an IRF4-deficient DT40 B cell line. We found that in the absence of IRF4, the expression of several molecules involved in BCR signaling was altered. For example, the expression of B-cell adaptor for PI3K (BCAP) was upregulated, whereas the SHIP expression was downregulated. These molecular unbalances were accompanied by increased BCR-induced calcium signaling, attenuated B cell linker protein (BLNK) and ERK activity and enhanced activity of PI3K/Protein Kinase B (Akt) pathway. Further, the IRF4-deficient cells showed dramatically diminished cytoskeletal responses to anti-IgM cross-linking. Our results show that IRF4 has an important role in the regulation of BCR sign...
European Journal of Immunology, 2006
The transcription factor Ikaros, a key regulator of hematopoiesis, has an essential role in lymph... more The transcription factor Ikaros, a key regulator of hematopoiesis, has an essential role in lymphocyte development. In mice, fetal lymphoid differentiation is blocked in the absence of Ikaros, and whereas T cells develop postnatally, B cells are totally absent. The significance of Ikaros in the B cell development is evident, but how Ikaros regulates B cell function has neither been established nor previously been studied with B cells that lack Ikaros expression. Here we show that disruption of Ikaros in the chicken B cell line DT40 induces a B cell receptor (BCR) signaling defect with reduced phospholipase Cc2 phosphorylation and impaired intracellular calcium mobilization, which is restored by Ikaros reintroduction. Furthermore, we show that lack of Ikaros induces hyperphosphorylation of Casitas B lymphoma protein subsequent to BCR activation. These results indicate that the absolute need of Ikaros for development, cell fate decisions and maintenance of B cells is due to the enhancement of BCR signaling.
Encyclopedia of Life Sciences, 2001
Rapid Cycle Real-Time PCR — Methods and Applications, 2004
Sub-cellular biochemistry, 2006
A key issue in understanding the hematopoietic system and B cell biology is to define the functio... more A key issue in understanding the hematopoietic system and B cell biology is to define the function of transcription factors. B lymphocyte development and function is controlled by a hierarchy of transcription factors including PU.1, Ikaros, E2A, EBF, Pax5 and Aiolos. Mouse knockout models provide information about the developmental and physiological importance of the disrupted gene. However, an early block in the development or a lethal phenotype prevents the studies of the functional importance of the gene at the later developing system such as the immune system. The chicken B cell line DT40 is used to circumvent these problems. Studies with DT40 have revealed a role for Ikaros transcription factor in B cell receptor signaling and Aiolos has been shown to regulate immunoglobulin gene conversion and cell survival. On the other hand, findings with Pax5 deficient mutants support DT40 targeting system as a valid model for the plasma cell differentiation and demonstrate the genetic plas...
European Journal of Immunology, 2010
Ikaros family transcription factors have a key role in lymphoid development, and their aberrant f... more Ikaros family transcription factors have a key role in lymphoid development, and their aberrant function contributes to a multitude of lymphoid malignancies. Ikaros and Helios bind to similar DNA sequences, and Helios associates with Ikaros-containing chromatin remodeling complexes. Previously, we have shown that loss of Ikaros leads to diminished BCR-signaling strength. In this study, we describe a Helios-deficient chicken DT40 B-cell line with a BCR signaling phenotype that is the opposite to that of Ikaros-deficient cells. In contrast to Ikaros-deficient cells, Helios À/À B cells exhibit increased calcium release to the cytoplasm after BCR crosslinking, but diminished BCR-induced phosphorylation of signaling molecules. The inositol 5-phosphatase SHIP, an important regulator in several signaling pathways, is differentially expressed in Ikaros-and Helios-deficient cells. In the absence of Ikaros, SHIP is upregulated, whereas Helios deficiency leads to the downregulation of SHIP expression. We also show with ChIP that Ikaros binds to the promoter of the INPP5D gene-encoding SHIP. Considering the critical role of SHIP in the BCR signaling pathway, our findings provide insight into the mechanism of how both Helios and Ikaros are involved in the regulation of BCR signaling.
Scandinavian journal of immunology, Jan 14, 2015
The graded expression of transcription factor Interferon Regulatory Factor 4 (IRF4) regulates B c... more The graded expression of transcription factor Interferon Regulatory Factor 4 (IRF4) regulates B cell development and is critical for plasma cell differentiation. However, the mechanisms, by which IRF4 elicits its crucial tasks, are largely unknown. To characterize the molecular targets of IRF4 in B cells, we established an IRF4-deficient DT40 B cell line. We found that in the absence of IRF4, the expression of several molecules involved in BCR signaling was altered. For example, the expression of B-cell adaptor for PI3K (BCAP) was upregulated, whereas the SHIP expression was downregulated. These molecular unbalances were accompanied by increased BCR-induced calcium signaling, attenuated B cell linker protein (BLNK) and ERK activity and enhanced activity of PI3K/Protein Kinase B (Akt) pathway. Further, the IRF4-deficient cells showed dramatically diminished cytoskeletal responses to anti-IgM cross-linking. Our results show that IRF4 has an important role in the regulation of BCR sign...
European journal of immunology, 2017
The transcription factor Bach2 is required for germinal center formation, somatic hypermutation (... more The transcription factor Bach2 is required for germinal center formation, somatic hypermutation (SHM), and class-switch recombination (CSR) of immunoglobulins. SHM and CSR are initiated by activation-induced cytidine deaminase (AID) which has potential to induce human B cell lymphoma. To understand the role of Bach2 in AID-mediated immunoglobulin gene diversification processes, we established a BACH2-deficient DT40 B cell line. We show that in addition to allowing SHM, Bach2 drives immunoglobulin gene conversion (GCV), another AID-dependent antibody gene diversification process. We demonstrate that Bach2 promotes GCV by increasing the expression of AID. Importantly, we found that the regulation of AID is independent of Blimp-1 and that BACH2-deficient cells have altered expression of several genes regulating AID expression, stability and function. Furthermore, re-expression of BACH2 or AID in Bach2KO cells restored the SHM and GCV defects. These results demonstrate that Bach2 has a ...
PloS one, 2016
The activation induced cytosine deaminase (AID) mediates diversification of B cell immunoglobulin... more The activation induced cytosine deaminase (AID) mediates diversification of B cell immunoglobulin genes by the three distinct yet related processes of somatic hypermutation (SHM), class switch recombination (CSR), and gene conversion (GCV). SHM occurs in germinal center B cells, and the transcription factor Bcl6 is a key regulator of the germinal center B cell gene expression program, including expression of AID. To test the hypothesis that Bcl6 function is important for the process of SHM, we compared WT chicken DT40 B cells, which constitutively perform SHM/GCV, to their Bcl6-deficient counterparts. We found that Bcl6-deficient DT40 cells were unable to perform SHM and GCV despite enforced high level expression of AID and substantial levels of AID in the nucleus of the cells. To gain mechanistic insight into the GCV/SHM dependency on Bcl6, transcriptional features of a highly expressed SHM target gene were analyzed in Bcl6-sufficient and -deficient DT40 cells. No defect was observ...
B lymphocytes constitute a key branch of adaptive immunity by providing specificity to recognize ... more B lymphocytes constitute a key branch of adaptive immunity by providing specificity to recognize a vast variety of antigens by B cell antigen receptors (BCR) and secreted antibodies. Antigen recognition activates the cells and can produce antibody secreting plasma cells via germinal center reaction that leads to the maturation of antigen recognition affinity and switching of antibody effector class. The specificity of antigen recognition is achieved through a multistep developmental pathway that is organized by interplay of transcription factors and signals through BCR.
Cell, Jan 18, 2014
AID mis-targeting is poorly understood but contributes significantly to B cell genome instability... more AID mis-targeting is poorly understood but contributes significantly to B cell genome instability. Two new papers in Cell reveal that AID mistargeting occurs primarily in gene bodies within a nuclear microenvironment characterized by high levels of transcriptional activity, interconnected transcriptional regulatory elements, and overlapping sense and antisense (convergent) transcription.
Scandinavian Journal of Immunology, 2011
Effective humoral immunity depends on B cells, plasma cells and follicular helper T cells (TFH) a... more Effective humoral immunity depends on B cells, plasma cells and follicular helper T cells (TFH) and secreted high-affinity antibodies. The differentiation of mature B cell into plasma cells is ultimately hardwired in a regulatory network of transcription factors. This circuitry is responding to extracellular stimuli, which leads to production of higher-affinity antibodies after germinal centre (GC) reaction. The understanding of the transcriptional regulation of GCs and the initiation of plasma cell differentiation is becoming increasingly clear. It is evident that transcriptional repressor Blimp-1 can drive the plasma cell differentiation, but the initiation of plasma cell differentiation in GCs is likely coupled to the loss of B cell characteristics maintained by transcription factors Pax5 and Bcl6.
The Journal of Immunology, 2013
Scandinavian journal of immunology, Jan 14, 2015
The graded expression of transcription factor Interferon Regulatory Factor 4 (IRF4) regulates B c... more The graded expression of transcription factor Interferon Regulatory Factor 4 (IRF4) regulates B cell development and is critical for plasma cell differentiation. However, the mechanisms, by which IRF4 elicits its crucial tasks, are largely unknown. To characterize the molecular targets of IRF4 in B cells, we established an IRF4-deficient DT40 B cell line. We found that in the absence of IRF4, the expression of several molecules involved in BCR signaling was altered. For example, the expression of B-cell adaptor for PI3K (BCAP) was upregulated, whereas the SHIP expression was downregulated. These molecular unbalances were accompanied by increased BCR-induced calcium signaling, attenuated B cell linker protein (BLNK) and ERK activity and enhanced activity of PI3K/Protein Kinase B (Akt) pathway. Further, the IRF4-deficient cells showed dramatically diminished cytoskeletal responses to anti-IgM cross-linking. Our results show that IRF4 has an important role in the regulation of BCR sign...
European Journal of Immunology, 2006
The transcription factor Ikaros, a key regulator of hematopoiesis, has an essential role in lymph... more The transcription factor Ikaros, a key regulator of hematopoiesis, has an essential role in lymphocyte development. In mice, fetal lymphoid differentiation is blocked in the absence of Ikaros, and whereas T cells develop postnatally, B cells are totally absent. The significance of Ikaros in the B cell development is evident, but how Ikaros regulates B cell function has neither been established nor previously been studied with B cells that lack Ikaros expression. Here we show that disruption of Ikaros in the chicken B cell line DT40 induces a B cell receptor (BCR) signaling defect with reduced phospholipase Cc2 phosphorylation and impaired intracellular calcium mobilization, which is restored by Ikaros reintroduction. Furthermore, we show that lack of Ikaros induces hyperphosphorylation of Casitas B lymphoma protein subsequent to BCR activation. These results indicate that the absolute need of Ikaros for development, cell fate decisions and maintenance of B cells is due to the enhancement of BCR signaling.
Encyclopedia of Life Sciences, 2001
Rapid Cycle Real-Time PCR — Methods and Applications, 2004
Sub-cellular biochemistry, 2006
A key issue in understanding the hematopoietic system and B cell biology is to define the functio... more A key issue in understanding the hematopoietic system and B cell biology is to define the function of transcription factors. B lymphocyte development and function is controlled by a hierarchy of transcription factors including PU.1, Ikaros, E2A, EBF, Pax5 and Aiolos. Mouse knockout models provide information about the developmental and physiological importance of the disrupted gene. However, an early block in the development or a lethal phenotype prevents the studies of the functional importance of the gene at the later developing system such as the immune system. The chicken B cell line DT40 is used to circumvent these problems. Studies with DT40 have revealed a role for Ikaros transcription factor in B cell receptor signaling and Aiolos has been shown to regulate immunoglobulin gene conversion and cell survival. On the other hand, findings with Pax5 deficient mutants support DT40 targeting system as a valid model for the plasma cell differentiation and demonstrate the genetic plas...
European Journal of Immunology, 2010
Ikaros family transcription factors have a key role in lymphoid development, and their aberrant f... more Ikaros family transcription factors have a key role in lymphoid development, and their aberrant function contributes to a multitude of lymphoid malignancies. Ikaros and Helios bind to similar DNA sequences, and Helios associates with Ikaros-containing chromatin remodeling complexes. Previously, we have shown that loss of Ikaros leads to diminished BCR-signaling strength. In this study, we describe a Helios-deficient chicken DT40 B-cell line with a BCR signaling phenotype that is the opposite to that of Ikaros-deficient cells. In contrast to Ikaros-deficient cells, Helios À/À B cells exhibit increased calcium release to the cytoplasm after BCR crosslinking, but diminished BCR-induced phosphorylation of signaling molecules. The inositol 5-phosphatase SHIP, an important regulator in several signaling pathways, is differentially expressed in Ikaros-and Helios-deficient cells. In the absence of Ikaros, SHIP is upregulated, whereas Helios deficiency leads to the downregulation of SHIP expression. We also show with ChIP that Ikaros binds to the promoter of the INPP5D gene-encoding SHIP. Considering the critical role of SHIP in the BCR signaling pathway, our findings provide insight into the mechanism of how both Helios and Ikaros are involved in the regulation of BCR signaling.
Scandinavian journal of immunology, Jan 14, 2015
The graded expression of transcription factor Interferon Regulatory Factor 4 (IRF4) regulates B c... more The graded expression of transcription factor Interferon Regulatory Factor 4 (IRF4) regulates B cell development and is critical for plasma cell differentiation. However, the mechanisms, by which IRF4 elicits its crucial tasks, are largely unknown. To characterize the molecular targets of IRF4 in B cells, we established an IRF4-deficient DT40 B cell line. We found that in the absence of IRF4, the expression of several molecules involved in BCR signaling was altered. For example, the expression of B-cell adaptor for PI3K (BCAP) was upregulated, whereas the SHIP expression was downregulated. These molecular unbalances were accompanied by increased BCR-induced calcium signaling, attenuated B cell linker protein (BLNK) and ERK activity and enhanced activity of PI3K/Protein Kinase B (Akt) pathway. Further, the IRF4-deficient cells showed dramatically diminished cytoskeletal responses to anti-IgM cross-linking. Our results show that IRF4 has an important role in the regulation of BCR sign...